A comparison of the functional parameters of operability in patients with post-inflammatory lung disease and those with lung cancer requiring lung resection

Background It is a common, yet unproven, belief that patients with post-inflammatory lung disease have a better functional reserve than patients with lung cancer when compared with their respective functional parameters of operability – forced expiratory volume in one second (FEV1), maximum oxygen uptake in litres per minute (VO2 max) and the diffusion capacity for carbon monoxide (DLCO). Objectives The aim of this study was to compare a group of patients with lung cancer with a group with post-inflammatory lung disease according to their respective functional parameters of operability. We also aimed to investigate any associations of FEV1 and/or DLCO with VO2 max within the two groups. Methods We retrospectively included 100 adult patients considered for lung resection. All patients were worked up using a validated algorithm and were then sub-analysed according to their parameters of functional operability. Results Two-thirds of patients had post-inflammatory lung diseases whilst the rest had lung cancer. The majority of the patients in the lung cancer group had coexistent chronic obstructive pulmonary disease (COPD) (n=18). Most (n=47) of the patients in the post-inflammatory group were diagnosed with a form of pulmonary TB (active or previous). Among the two groups, the lung cancer group had a higher median %FEV1 value (62.0%; interquartile range (IQR) 51.0 - 76.0) compared with the post-inflammatory group (52%; IQR 42.0 - 63.0; p=0.01). There was no difference for the %DLCO and %VO2 max values. The lung cancer group also had higher predicted postoperative (ppo) values for %FEV1 (41.0%; IQR 31.0 - 58.0 v. 34.0%; IQR 23.0 - 46.0; p=0.03, respectively) and %VO2 max (58.0%; IQR 44.0 - 68.0 v. 46.0%; IQR 35.0 - 60.0; p=0.02). There was no difference in the %DLCO ppo values between the groups. Conclusion Patients with lung cancer had higher percentage values for FEV1 and ppo parameters for %FEV1 and %VO2 max compared with those who had post-inflammatory lung disease. Our findings suggest that lung cancer patients have a better functional reserve.

Lung resection can be a high-risk procedure, especially in patients with underlying cardiopulmonary disease.Predictors of mortality include the extent of resection, comorbidities and cardiopulmonary reserve. [14,15]inety percent of lung cancer patients are current or past smokers, which is frequently associated with varying degrees of concomitant chronic obstructive pulmonary disease and/or ischaemic heart disease.Furthermore, many of these patients are of advanced age and this places them at an increased risk of post-operative complications and mortality. [16,17]A number of prospective studies have validated a percentage-predicted forced expiratory volume in one second predicted postoperative value (%FEV 1 ppo) of <40% as a prohibitive threshold for pulmonary resection, with mortality rates as high as 50% in such patients.Ferguson et al. [18] demonstrated that a diffusion capacity for carbon monoxide (DLCO) of <60% of the predicted value was a cut-off value for major pulmonary resection.The maximum oxygen uptake in litres per minute predicted postoperative (VO 2 max ppo) value of <10 ml/kg/min, obtained from either formal cardiopulmonary exercise testing (CPET) or low-technology (minimal achievement) exercise tests, is associated with a high risk of post-operative complications and death.Regarding the cardiac

A comparison of the functional parameters of operability in patients with post-inflammatory lung disease and those with lung cancer requiring lung resection
M H Amirali, MD, MMed (Int), FCP (SA); E M Irusen, MB ChB, FCP (SA), FCCP, PhD; C F N Koegelenberg, MB ChB, MMed (Int), FCP (SA), FRCP (UK), Cert Pulm (SA), PhD risk assessment, the Revised Cardiac Risk Index (RCRI) [19] is used by many authorities.The criteria contain six independent variables that correlate with post-operative cardiac complications -these include a high-risk type of surgery, a history of ischaemic heart disease, cardiac failure, cerebrovascular disease, diabetes requiring treatment with insulin and pre-operative serum creatinine of >177 µmol/L.Patients with more than two variables have a postoperative cardiac complication rate >10% and are considered to be at high risk. [17]he validated algorithms used to assess candidates for lung resection are based on spirometry, the DLCO and the VO 2 max. [14]ne such algorithm proposed by Bolliger and Perruchoud [15] has been used widely as a tool for evaluating cardiorespiratory reserves of lung resection candidates.The algorithm proposes that patients undergo successive steps of functional testing, the results of which qualify them for varying extents of resection or alternatively preclude them from any surgery. [15]part from the underlying cardiopulmonary disease and other comorbidities, the calculated predicted postoperative (ppo) values for FEV 1 , VO 2 max and DLCO are directly proportional to postoperative functional state and mortality. [21]t is a commonly held belief by various experts in the field of pulmonology that patients with post-inflammatory lung disease have a better functional reserve postoperatively than patients with lung cancer, when comparing their respective FEV 1 , VO 2 max and DLCO values; however, there is limited evidence to support the belief. [16]he aim of the present study was to compare two groups of patients (i.e.patients with lung cancer v. patients with post-inflammatory lung disease), and to investigate the association of functional parameters of operability within these two groups of patients.

Study design and population
We retrospectively enrolled adult patients who had been considered for lung resection and were referred to the Division of Pulmonology at Tygerberg Academic Hospital, Cape Town, with either lung cancer or post-inflammatory lung disease.Ethical approval for this retrospective analysis was obtained from the Stellenbosch University Research Ethics Committee (ref.no.S15/04/074).The application included a waiver of consent due to the retrospective nature and anonymity of the study design.
Cases were identified from existing medical records; they were stratified into two groups, namely ' A' and 'B' , where ' A' comprised patients with non-small-cell lung cancer while 'B' comprised patients with post-inflammatory lung disease (bronchiectasis, active/post tuberculous haemoptysis, and aspergilloma).After obtaining permission from the chief medical superintendent, the original medical records of all cases identified were requested and data were collected anonymously.The data collected included the demographics (age, gender), comorbidities of patients, indications for lung resection, extent of lung resection, and their pulmonary function test values (i.e.FEV 1 , FVC, DLCO and VO 2 max).The ppo value for these parameters can be calculated by the equation in Fig. 2, where the pulmonary function test (PFT) can either be %FEV 1 , %VO 2 max or %DLCO.We used three validated ways of estimating the relative functional contribution or split function, i.e. anatomical calculation, split radionucleotide perfusion scanning and quantitative computer tomography scanning and dynamic perfusion magnetic resonance imaging (MRI).
Anatomical calculations of ppo values were performed on all patients who required pre-operative estimation of post-operative lung function.Patients who required further evaluation underwent either radionucleotide perfusion scanning or quantitative CT scanning.All patients were worked up for lung resection using the algorithm for the assessment of their cardiorespiratory reserves (functional operability). [17]Patients were generally followed up as outpatients and CPET was only performed once the risk of haemoptysis was Both <40% <35% or <10 mL.kg -1 .min -oth >80% Fig. 1.Algorithm proposed by Bolliger et al., [15] adapted by Koegelenberg et al. [17] (ECG = electrocardiogram ; FEV 1 = forced expiratory volume in one second ; DLCO = diffusion capacity for carbon monoxide; VO 2 max = maximum oxygen uptake in litres per minute; mL = millilitres; kg = kilograms; )

%PFT ppo = [%PFT -((a/n) × %PFT)] × 100
where PFT = pulmonary function test a = number of segments to be resected n = total number of segments RESEARCH evaluated (i.e. no haemoptysis for 2 weeks).Patients included in the study were then evaluated for their respective functional operability parameters.

Statistical analysis
χ 2 comparisons and Pearson product-moment correlation coefficient (Pearson's r or 'r-squared') of proportional data were performed.We did not make any assumptions for normality; hence, these nonparametric inferences were used for statistical analysis.A p-value <0.05 in a two-tailed test of proportions (χ 2 ) was considered statistically significant.Unless stated otherwise, data are displayed as median with interquartile range (IQR) values.

Results
We included 100 patients in our study.The demographic data, primary diagnoses and comorbidities of the patients are summarised in Table 1.The majority of our patients were male (n=66/100); 51 were diagnosed with a post-inflammatory lung disease, while the rest had lung cancer.
The most common diagnosis in the post-inflammatory group was that of haemoptysis (n=47).Bronchiectasis and aspergilloma were the second most common diagnoses, followed by post-TB bronchiectasis and destroyed lung.
The majority of the patients in the lung cancer group had COPD (n=18), 11 of them were either active or previous smokers.Two of the patients had ischaemic heart disease.Most (n=47) of the patients in the post inflammatory group were diagnosed with some form of pulmonary TB (active or previous).COPD and smoking had the second and third highest prevalence, and 17 patients had no associated comorbidities.

Table 1 . Demographic and clinical data of study population
*Unless otherwise specified.